Radiophone communication system



JUL 9, 1940- w. J. SCHNELL 2,186,500

` nADoPHoNE coMMUNIcATIoNWsYsTBM K Filed Aug. 6. 1957 2 sheets-sheet 1 f/czj.

Jan. 9, 1940. w J, SCHNELL* 21,186,500

`RADIOPHONE COMMUNICATION SYSTEM FiledAug. s, V1957 `2 Sheets-sheet 2 16 0 11e ll@ 154' 140 y ,j V145 /G a4 5T E6 76j/ ,Jzol/ 133' 156 I u ev 90.95'- Ja? f 114 M.156 Ze,1,"bl|6y 6E* 14/55 @o f ..m o

105z 1| 130 15a 74,/ lj1 153 IZ 139. [017 Y 0 A E DETE'CTOR ma 13B wat Jaz' 74106 wb @150150 19g-L ,am 56' Patented Jan. 9, 1940 y UNITED! vSTATI;

Wiuiam J. sehnen; Berwyn. nl., assigner to niet. f

,trical Research Laboratories,`lnc.,"hlmo, ma;

a corporation oilllinois f f Application August6, 1937, 1s claims. (o1.` 11s- 1) invention relates -to fav combined radio receiver and telephonie system."

An object of this invention is to provide a lcommunication system in which'a radioreceiven. Y

comprising the usual reproducer',v and a remotely positioned reproducer may be selectively controlled to permitY two-way telephonic communication between the receiver and the remotelypositioned reproducer. Y

Another object oi the invention isfto provide means by which a radio receiver may be se-.

lectively controlled to transmit radio signals :to Y a remotely positioned reproducer andto estab` lish' telephonie communication between-persons Another object of the invention is to provide,

',ception of radioy signals; that when the pointer" at the receiver and personsv at the remote-point. Y `to the receiver; and that when the pointer 'faces vthe sector 26 the systemis adjusted fork transe' in connection .with the above stated system.'H

means by which a calling signal may be transmitted from the remote point to the radio. re-

ceiver. Another object of the invention resides in theprovision oi a control unit readily connectable to substantially any radio' receiver andV toV a reu motely positioned reproducer by which said receiver and reproducer may be adapted for telephonic communication between remote pointsy winch control unit shall be simple, compact in construction, eilicient inoperation and` inexpensive in cost. y .v

Other and further objects and advantages oi the invention will be apparent from vthe following description when taken in connection with the accompanying drawings, wherein:

Fig. 1 is a view in perspective of the units form-y ing a combined radio receiver and telephonie con'lmunicationsystem in accordance with applicants invention.

Fig. 2 is a schematic representation of the electric connections of the external units.

y o Fig. 3 is a diagrammatic view in perspective of a control switch forming atpart of the control unit.

Fig. 4 is a perspective view of a call signal control switch forming a part of the invention'. As shown Ain Fig. l, the invention comprises a radio receiver 2 of any suitable conventional structure; a sound reproducer or loudspeaker 4 normally forming a part of such receiver and which, as hereinafter to be described, is also emciated with the reproducer-micrcphone 6; and

ployed as a transmitter or microphone; are-- motely positioned soundr `reproducer or loud-v I4 and is rotatably supported in suitable brackets a control /unit' I2 preferably adjacent the radio' receiverxz'. 'i y n The.,control:unitililcorriprisesjanhmising-Bitg onthe front panelof ,which is mounted 'a suitable strip I6 carrying` functional indicia representing '15 thecondition of lthe system `for dicerent settings,v of vaA manually operable knob I8 and-pointer 2o. v' Such indicia carrying stripv I6 may, iorjexample, comprise a sector `22 marked Radio, a sector* 24 markedA Listen, yand a sector 26 marked'V l@ Talk, vindicating that when the pointer faces the sector 2 2 the systemis adjusted for ,ther re faces the Asector 24 the system Vis adjustedior transmission of4 messages fromvv the remote point mission of messages lfrom the control station to the remote point.- j

The manually operable vknob I8` andpointer 26 are carriednon the projecting end oi a shaft 28 (Fig. 3) of a kswitch means V3i). :The shaft passes throughY the front panel of the housing (not shown) rwithin said housing.rv The control unit Y I4. comprises, in addition to the elements described, connecting means or cables 32, 34 'and 38 and -a socket 38. The cable 32 is connectedv .en d to afplug`40 adapted to be inserted into 4vthe at one end to the control unit and at its other usual socket 42 providedlfor the reception vci the speaker plug. The cable 34 is also connected at one end to the control unit 'and carries atv its ,other end suitable connecting plugs or tip jacks 44 and 46 adapted to be inserted into suitable sockets 46 andh secured to the chassis of the radio receiver and connected in the circuitof the latter ina manner later to be'deseribed. 'I'he cable as. is likewise'connected at one end to the control unit I4 and at its other end tetheremotely rpositioned 'reproducer-microphone 6. If desired, the cable 36 may terminate' in a Asuitable socket yadapted to detachably receive the usual connecting plug associated with a loudspeaker. j The socket 38'is adaptedfto receive the usual speaker plug carried'on the free end ofthe connecting cable 62 of the speaker or reproducermicrophone 4.Y i 1 On the wallsof the housing for theV reproducer-microphone 6, or on a separate support associatedtherewith, is mounted; in any desired `manner the calling device or buzzer .8- anda battery-or set of y'batteries 54. as for example, a pair-of ash light batteries, energizing the buzzer 6." The buzzer` may be of any desired type, for

assiette.

l example of a kind adapted to operate at the low voltage provided by a pair of small ash light batteries connected in series. f Y

The switch |8 ymay be of any conventional structure providing a simultaneously operable single-pole,v double-throw switch element and a single-pole, single-throw switch element. As shownl in Fig, 4, the switch |8 selected for illustration comprises a pair of movable contact blades 56 and 58, the blade 56 being adapted` selectively to engage fixed contacts 68 and 62,. and the blade 58 being adapted to engage a fixed contact 64 when the blade 56 engages the fixed contact 62. Suitable insulating blocks 66 are provided between each of thexed and movable contacts.

The operating means for the switch |8 may comprise a push button 68 slidably supported in one wall of the speaker housing or other supporting plate, the blades 56 and 58 by reason of their resiliency normally retaining the button 68 in its extended position-in which position 'the vblade 56 engages the contact 68 but the blade 58 is out of engagement with the contact 64.

The switching means 38 controlled by the shaft 28 of the control unit |2 comprises, in the illustrative embodiment, nine movable contacts 18 to 86, with each of which is associated a group of fixed contacts. The movable contacts 18 to 14 maybe secured to the face of an insulating disk 88 adjacent the periphery thereof and angularly disposed'as shown in Fig. 3. The insulating disk 88 is secured to the shaft 28 for rotation therewith.

Thethree groups of fixed contacts comprising nine contacts 88 to |88 nry be mounted on an insulating disk |88 supported by spaced rods ||8 and ||2, which rods may be supported in any suitable manner (not shown) within the housingY |.4. 'I'he three movable contacts 16, 18 and 88 are similarly mounted on an insulating disk ||4 secured to the shaft 28 for rotationy therewith,

`and the three groups of xed contacts comprising contacts H6 to |32'associated with said movable contacts may be mounted on an insulating disk |34 also supported on the rods ||8 and 812;-

The three movable contacts 82, 84 and 86 are likewise mounted on an insulating disk |36 secured to the shaft 28 for rotation therewith and the three groups of contacts comprising nine contacts |38 to |54 are mounted on a disk |56 similarly supported by the rods ||8 and |2.

It should be noted that the'mcvable contacts are simultaneously operable to engage their corresponding rst, second or third xed contacts, and that the switch means 38 therefore comprises in substance nine single-pole, triple-throw switches simultaneously operated to the correspending positions by the shaft 28 and manually operable knob |8. y

Means are provided for normally retaining the shaft 28 and each of the movable contacts in the positions shown in Figs. l and 3 wherein each of the movable contacts engages the first contact of its group of three contacts and wherein the pointer 28 .is alined with the Radio sector 22. This means comprises a lever |58 secured to the inner end of the shaft 28 and a spring |88 secured to the outer end of the lever |58 and to a suitable pin carried by a lug |62 formed on or secured to the base of the housing I4. It will be evident that the spring |68 moves the shaft 28 in a counterclockwise direction, as seen in Fig. 3, and normally retains the switches in the positions shown in saidfigure.

In Fig. 2 are schematically illustrated the connections between the switch means 38 of the control unit |2 and the other units of the system. Certain of the circuits of the radio receiver are schematically represented in said figure for the'purpose of showingthe connections of the control unit to said receiver.

As shown in said figure, the circuits of the radio receiver comprise a detector |64, the input of which is connected in the conventional manner to the usual high frequency amplifier, which 1n turn is connected to a suitable antenna. The

coupling between the detector |64 and the tube |66 forming the first stage of amplification of the audio-amplifier comprises a Volume control resistor or potentiometer |68 grounded as at |18 -and adjustably connected by the lead |12 to the grid of the audio-amplifier |86. The sockets 48 and 58 for receiving the plugs or tip jacks 44 and 46 are inserted into the lead |12 and are connected by a resilient contact strip |14 which is adapted to break the direct connection between the sockets 48 and 58 when the tip jacks 44 and 46 are inserted therein. Upon removal of the tip jacks 44 and 46, the resilient contact strip |14 automatically connects the sockets 48 and 58 and directly connects the grid of the tube |66 with the volume control resistor |68. 'I'he location of the sockets 48 and 58 between the volume control resistor and the grid of the tube |66 is of importance because such location eliminates the need of adjusting the volume control when the radio receiver` is used for telephonie communication purposes.

Subsequent stages of audio-amplification are indicated as an amplifier |16. The amplifier |16l is connected in the customary manner by a transformer |18 to the input of a power amplifier |88, which preferably comprises a pair of power tubes |82 and |84, the grid and cathode electrodes of which are connected in conventional manner to the transformer |18 in pushepull. The output leads |86 and |88 from the plates of the tubes |82 and |84, respectively, are connected to suitable plug-receiving contacts associated with the socket 42. A lead |88 connects the positive side of the B voltage supply source to one of the plug-receiving contacts of the socket 42. The elements just previously described, with the exception of the plugs 48 and 58 and the resilient strip |14 connecting said plugs, comprise any usual radio receiver.

y, The cable 34 connecting the tip jacks 44 and 46 to the control unit preferably comprises two wires- |92 and |94, the Wire |92 connecting the tip jack 44 to a wire |96 connected to the movable contact 18 of the switch means 38 and the wire |84 connecting the tip jack 46 to a wire |98 connected to the movable contact 86. A condenser 288. of the order of Winoo of a microfarad, is interposed in the wire |98 and a resistor 282 of the order of 100 megohms is connected be' tween the wires |98 and |86 at a point in advance of the condenser 288.

The cable 32, which is adapted to connect the receiver socket 42 to the control unit preferably comprises three wires 284. 286 and 288, the wire 284 connecting the plate lead |86 to a wire 2|8 connected to the movable Contact 12. The wire 286 connects the positiveB supply lead |98 to a wire 2|2 connected to the movable contact 18 and the wire 288 connects the plate lead |88 to a wire 2|4 connected to the movable contact 14.

' other endof -the transformerv isrconnectedl The cable 52, which connects the reproducing f n wires 216 and 218 to one side of: the battery 54 microphone or loud speaker 4 to the control unit,

preferably `comprises threerwires 2 I 6, 2 I8 .and 220.

The wire 2|6 connects one end lof the primary winding of thc speaker transformer 22,2, the`-` secondary of ,which is connected tothe speaker Voice coil 224, to a wire 226.

ciated with the movable contact 12. The wire 2 8 connects the midpoint ofA thc4 primary of, the speaker transformer 222 withra wire'228, which in turn is connected. to thexed contacts |22 and |24 associated with the movablelcontact'l. v.The wire 220 connects the other end ofthe primary of the transformer 22 with the xed Contact |44 associated with the movable contact 84.

The cable 38, connecting the remotely located reproducer-microphone or. loudspeaker 6 with the controlV unit, preferably. comprises` vthree wires-232, 234 and 236, the wire 232` connecting one end of the primary winding ofl the speaker transformer 238 to a wire y24|! connectedto the xed Acontact |52 associated with the movable contact 88.

a wire 244 connected to the xed contacts |62A and |66 associated with the lmovable contact `14.`

Suitable interconnectionsare provided withinH the control unit and these interconnections are A wire 246 connects the xed,

made asfollows. contacts 92 vand 94 associated with the movable contact 16 with a condenser 248; the other" side of the condenser ,being grounded as at 256. j A

jumper 252 connects the movable contact'16 to c the ground connection at 250. A lead 254 con-,-

nects the movable contact 82 Vwith the Xe-d' con# tact ||8 associated with the movable contact16. A wire 256 connects this lead withthe wire 244; A jumper 258 connects the iixed contacts |2.'I and |38 associated with the movablecontacts 16 and the movable contact 88.

82, respectiveli, and a wire .260 connects ,thisA jumper to the wire 226.

A lead 262-interconnects the xedcontacts 96 and |00 Vassociated with the movable contact-12 with the movable -contactil! and a jumper 264 connects the lead 262 with the fixed contact |52 associated with the movable contact 88 and with the wire 240. lead wire 2| 2 and the movable contact 18 with A wire 268 connects the xed Contact |44 associated with the movable contact 84 with the xed contact |54 associated with the movable contact 66 .and a jumper 218 connects the wire 236 with the xed contact |04 associated with the movable contact 14. The wire 212 connects the xedcontact |59 associated with the movable contact 66 to the wire |86 and the movable contact 16.

Certain of thexed contacts, viz., the contacts 90, ||6, |26, |36,` |40, |42, |46 and |48 are not connected to any othercontactror lead, 'these contacts being shown in thedrawings for theV purpose of clarity of description andbecause there will be less likelihood of error in assemblingthe switching means 30 if all'of the supporting disks, |08, |34 and |56,'are identical andprovided with identical arrangements of contacts.

Within the housing ofthev reproducer-microphone or loud speaker 6; the secondary of the transformer 238 is connected a t one end bya wire 214 to the contact plate 56 of the switch |0. The

I The wireh226tis' connected to the central fixedlcontact'flilY asso- The wire234`conn'ects themidpoint v of the primary winding` of the transformer 238,

` contact v|10.

A jumper 266 interconnects thev and to-one side of the usual. voice coil ,280, Y'i'.'he

other side of -thefbatteryfis vconnected to the Y i' contact-64 Vand lthe otherside of the voicecoilfis,

connected to the fixed contact. 60..

The coirzaz` of the buzzer vais connecteavbe-V.

the buzzer coil connectedto the `fixed,contact 62. The'variouscircuits completed'by the controlr unitin the three different positions ofthe switchl ling means snare as follows. mwah the `switch in fthe, position 'showin vin 3 Feach movable 1 contact will bein engagement'with its :first flared contact." The'lead |12 from'the potentiometer l |68 will beconnected to the gridof ertube. |664-r through the socket 48, thef tip jack 44, wires $62 las and; 212 to the xedemtact |50. and'from the xed contact |56 through' the movable conc.

tact 86j awire |98',condenser'200, wire |64, tip.

jack 46 and socket`50. The receiver is therefore;y 1'

adjusted'for ythe passage of radio "signalspfromthe detector tothe power output amplier ,180.2

Radio signals in the output oithepower ampliier are ytransmitted to the reproducer-mi--` operating as a loudspeaker."l

output of the power amplifier '|80rflows fromrthey positive source of' B voltage 'supply through ythe Wires 49o; 20s, andffzlz to the moverme, Contact 18, `and through 'thejumper266 to the :movable From the movable contact 18 current passes -by way ofthe xedcontact |22,the.`

wire-228 and the wire-U8 to the -midpointvof the t primary winding of the transformer 222. ,Cura

rent'returns from thef transformerf222 by wires 2|6, 226,260', 258', xed contact |38, movable' conf:

tact 82, jumper 254,' wire 256, xed contact |02, movable contactf14,"wire 2'|4, wire.208'and the, f wire |88 to the plate of the-tube |84;

the output of the power amplifier |80rare-.imf-f pressed on the reproducer-mic-rophone"4 acting4 as a loud speaker. The circuit/to the reproducermicrophone 6 is completed from vthe positive'sid'e of the Bj supply voltage through wires |90,` 206, 2|2, 266,movable contact 80, xed contact |28, wire 242 and wire' 244 to the vmidpoint ofthe primary of the transformer 238. From one end of this primarythe current is returned through wire 232, wire 240,-wire264,`wire 262, xed contact 96, movable contactv 12, wire 2|0. wire `204 and wire |86 to the plateof thetube |82; From the other side of the primary of the transformer 238the current returns through VWire 236, wire 244, x-edfcontact |02, movable'contact 14; wire 2|4, wire 208 and wire |88 Vto the' plate of the tube |84. f t

, The secondary of the transformer 238, with the push button 68 in its normal extending position, is connected to the voicecoil y260 through the wire 214, switch blade 56, fixed contact 60, the voice coil 280 and-the wire 218. It will therefore be seenV that radio signals in the output of the powerairiplier |80 will-be transmitted to. and impressed kupon the reproducer-microphone 6 voperating asia loud speaker.

the interrupter 284 of now acting as a primary,

260 and the wire With the switching means inthe position ,fshown in Figs. 2 and 3 for the completion 'of the circuits just described, the push button 68 associated with the remotely positioned switch |0 maybe operated to impress upon the speaker 4 a calling signal voltage. The push button 68, when depressed, connects the free end of the buzzer 8 to the wire 214 by means of the fixed contact 62 and the switch blade 56 and connects the buzzer 8 to the battery 64 through the fixed contact 64 and the switch blade 68. The interrupted currents provided by `the'buzzer 8 are therefore applied to the secondary ofthe transformen 238, which secondary is and these currents are by induction transferred Vto the primary thereof and supplied to the wires 232 and 236. The current flows over the wire 232 through the -wire 240, the wire 264, the movable contact 84,the xed contact |44, the Wire 230 and the wire 220 leading to the speaker 4 associated with the radio receiver. Current supplied by the wire 236v passes through the wire 244, kthe wire 256, the wire 254, the movable contact V82, the jumper 258, the wire 226 to 'the wire 2|6 leading to the other side of the primary winding of the transformer 222 associated with the loud speaker 4. `The buzzer 8 at the remote point thereby impresses upon the loud speaker 4a calling signal 30 signifying that Va person at the remote point desires to communicate over the system with a p'ersony at the radio receiver.

Withthe switching means 30 in its intermediate position, each of the movable contacts will engage the intermediate fixed contact, thereby connecting the reproducer 6 at the remote point in the grid circuit of the tube |66 of the radio receiver and maintaining the reproducer-microphone 4 connected to the output power amplifier |80.. These connections are accomplished as follows. The wire 232 from the remote speaker is vconnected by the wire 240, the fixed contact |52, the movable contact 86, the wire |98, the condenser 200, the wire |84, the tip jack 46 and the socket 60 to the grid of the tube |66. The wire 236 leading from the remote point is connected by the wire 244, the wire 256, the fixed contact I8, the movable contact 16, and the wire 262 to ground at 250. The lead |12 from the potentiometer |68 is connectedby the socket 48, the tip jack 44, the wire |62, the wire |96, the movable' contact 10, the fixed contact 92, the wire 246 and the condenser 248 to ground at 260. It will, therefore, be seen that voice current fluctuations produced in the voice coil 280 by vibration of the daphragm of the reproducing microphone 6 will be impressed upon the grid of the tube |66. The connection between the power amplifier and the reproducer-microphone 4, still operating as a loud speaker, will be maintained through the wires 2|0, 2|2, and 2|4. The wire 2|0 is connected to the wire 226 leading to the speaker 4 by the movable contact 12 and the fixed contact 88; the wire 2|2 is connected to'the wire 228 leading to the speaker by the movable contact 18 and the fixed contact |24; and the kwire 2|4 is connected to said speaker by the movable contact 14, the fixed contact |04, the wire 210 and wire 268 to the speaker wire 230 at the fixed contact |44. It will therefore be seen that telephonic communication may be established between a person at the remote reproducer-microphone 6, now operating as a microphone, and a person at the reproducer-microphone 4.,. now operating as a loud speaker, the communication being established through the audio and power amplifier of the radio receiver. l

In this position of the controlling switch 30, operation of the switch |0 connects the buzzer 8 to the transformer 238 lin the manner previously stated and the interrupted voltage generated by the buzzer 8 is impressed in the grid circuit of the tube |66 and, by the audio and power amplifiers of the radio receiver, impressed on the speaker 4, thereby providing ay signal indication that the called person is present at the remote point.

When it is desired to establish telephonie communication in the opposite direction, the switch- Ving means 30 is operated to cause eac-h of the movable contacts to engage the third of its associated fixed contacts. With the switch in this position the reproducer-microphone 4 will be connected in the grid circuit of the tube |66 and the reproducer-microphone 6v will be connected in the output of the amplifier |80.

These connections are established as follows:

The wire 2|6 from the reproducer-microphone 4,

now operating as a microphone, is connected by the wire 226, the Wire 260, the fixed contact |20, the movable contact 'I6 and the wire 252 and to ground at 250. The wire 220 from thespeaker 4 is connected by the wire 230, the wire 268, the fixed contact |54, the movable contact 86, the Wire |68, the condenser 200, the wire |84,

' tip jack 46, and the socket 50 to the grid of the tube |66. The wire 232 from thereproducermicrophone 6, now operating as a loud speaker is connected by the wire 240, the Wire 264, the wire 262, the fixed contact |00, the movable contactV 12, and the wire 2|0 to the wire 204 connected by the wire |86 to the plate of the tube |82.V The Wire 236 from the speakerV 6 is connected by the wire 244, the fixed contact |06,

the movable contact 14, and the wire 2|4 to the Wire 208 connected by the wire |88 to the plate of the tube |84. T'he B supply voltage for operation of the tubes |82 and |84 and the speaker- 6 is supplied from vthe lead |90 bythe wire 206, the wire 2|2, the wire 266, the movable contact 80, the fixed contact |32, the wire 242, and the wire 234 to the midpoint of the primary of the transformer 238. It will therefore be seen that in this third position of the control switch 30,

telephonie communication may be established` between the person at the speaker 4, now operating as a microphone, and a person at the remote reproducer-microphone, now operating as a speaker. i

When the reproducer-microphone 4 is operating as a microphone, operation of the switch|0 is ineffective to impress a calling signal on'said microphone, the wires 232, 234 and 236 from the speaker 6 being disconnected from the wires 226, 228 and 230 leading to the reproducer-microphone 4 at the movable contacts 12, 18 and 14. This, therefore, prevents interference with the reproducer-microphone when the same is operating as a microphone.

It will be evident therefore that applicant has provided an lefficient means of striking simplicity by which a radio receiver maybe selectively controlled to transmit radio signals to a remote point and to establish two-way telephonie communication between a person at the receiver and a person at the remote' point.

Changes may be made in the form, construction and arrangement of theparts without departing from the spirit of the invention or sacrificing any of its attendant advantages, and the right is hereby reserved to make all such faisatoo i l -5 changes as fairly fall within the scope of the followingclaims. 'l o l' 1 The invention is herebyclairned as 'followszx 1. In combination, a radio receiver comprising: a signal circuit land a reproducer, a secondY re-A producer locatedat a point remote from said receiver',-V and'la control unit for selectivelyconf necting both of said reproducdsers in the-output Vof saidV circuit lor one ofv said'reproducerslin vthe output of said circuit and the other of said reproducers to'anintermediate point in `saidcircuiti whereby radio or two-way telephonie communi-r 1 tablished'with the remote cation 1s selectwey es y thej remote` reproducer,y said switchingmeans ,being operable selectivelyto connect veitherfollie y f` y0f said reproducersrin:theoutputotsaid Signal point by means of` said radioreceiver.

v2. In combination,y a vradio receiver comprising' a detector, an'audio-amplier anda reproducer.'

tively connecting both of said reproducers in the output of saidwamplier andsaid detector to the input'of said amplier, or one 'of-said reproducers in the outputoof said ampliiier and@A Athe other of said reproducers `in the input of'v said'amplier whereby radio signals may be re produced at the receiver'and at the remote point andftwo-Way telephoniccommunication may be y Y y y. a control unit comprising switch means,y means established with the remote-point. 1

-3. In combination, a radio receiver comprising a signal circuit anda reproducer, `a second` reproducer locatedrat arpoint remote ,-from fsaidz. receiver and a control unit for `selectively connecting both of saidreproducers in `the voutput of said signal :circuit or one of said reproducers ducer, saidswitch means being operable selec-, y tively-to connect bothj of said' reproducers .in-the in the output of said circuitfand the other of said reproducers to an-*intermediate point of said circuitvwhereby radio signals maybe reproduced at the receiver and at the remote' point and two-way telephonie communication' may be established with the remote point, and means for transmitting a calling signal rfrom one reiproducer to the other. 1

4. In combination, a radio receiver comprising a. signal circuit and areproducer, a second i a signal circuitinthe output ofA which is ,confl reproducer located at a point remote'from" saidreceiver, and a control unit for selectively 'iconnecting both of said reproducers in the output of said circuit or one of said reproducers in theV output of said circuit and the other'of said reproducers'to an intermediate point of :said circuit whereby radio signals 'may be-reproduced at the receiver' and at the remote point and"r two-way telephonie communication may be established with the remote' point, a call signal reproducer to impress a calling signal on the iirst reproducer.

5. In combination, a radio receiver comprising a signal circuit and a reproducer, a second re` producer located at a point remote from said receiver and a control unit'for selectively connecting one ofsaid reproducers in theoutput of said circuit and theother of saidy reproducers to an intermediate point of said circuit whereby two-way telephonie communication is `established with'the remote point, callingfmeans'at the remote point, and -means operable when theremote reproducer is connected to the intermediate point of s'aid signal circuit for connecting saidy calling means to said intermediate point and operable when said remote reproducer isc'onnected in the output of said signal circuit to connect said calling means-directly tothe rey 7U Producer of the receiver. A

y6. lIncomlriination with av radio receiver having a signal f circuit, in the-outputot .which is c.

ing .a vparti of the receiver, a second reproducer connect said.'Y switch means.V tothe output ter# o minal means of the receiverrmeans toconnect. v 'the' Vswliiiclnmeans to-uan, intermediate point of; -thegsignal circuitfmeansftoconnecttheyswitci'i 's g ing means ltothe@reproducer of the receiver,

and means v.to Vconnect said switching .means to v circuit and the other of said reproducersto the Withthevremotepoint.

7.a.Incornbination with a radio receiver having Y a signal circuit,v in the output' of which is c'fofn-` I c ive the terminalmeans Vof a'klprodu'cer form,

located at'` la point remote `from vsaid receiver.

.nected terminal'means adapted to detahably reto connect'said switch .means to the output teit-fl.y

signal circuit, means to connect the switcnmeans connect said switch meansl to theremote repro output of said circuit orv either onelof, saidu repointof said circuit, whereby radio-signals may be .simultaneously transmitted to, s aidvrepro-I. Y a ducers ori two-way.l telephonie. vcommunication l may be established'with the remote point.

` to the-reproducer offthe receiver and means to l f 'producers in the output of said circuit and the', 'other of 'said reproducers to fthe intermediate B. In combination kwith a radio receiver having nected vterminal means adaptedv to detachably receive the terminal means of the reproducer forme means of` the receiver, means to connect the switch means toan intermediatepoint of the i. I y

ving a part ofthe receiver, a secondreproducer locatedr at ya vpoint remote from said receiver,y a control unit comprising switchmeans, ymeans to f connect said switch means `to the output terminal ,'50

signal circuitfmeansto connect the switch means tothe reproducer of thereceiver, and `means to connect said A:switch means to thefremotev reproducer, said switch means being operable selec"V tively to connect both'of said reproducers in the output :of saidcircuit oreither oneof=,said re-fproducers in the outputl of said circuit andl the other of l said reproducers to vthe intermediate I point'of said circuit whereby radio signals mayl be simultaneously transmitted to said reproducers or twoway telephonie communication maybeesf tablished with the remote point, and meansfor normally retaining said' switch means in; such `position that bothV of said reproducers are connected thereby in the outputof the signal circuit.

9. In combinationwitha radio receiver comv prising an amplifier, volume control means in the input .of 4said. amplifier Aand a reproducer, -a second reproducer located at apoint remote from said receiver,Y and a control unit forA selectively connecting both of said reproducers in the out put of `said signal circuit or either `one of s aid re-v producers inv-the input ofsaid amplier between of the amplifier, and the other of said reproducer'svin the output of said amplier whereby radio signals may be reproduced at the receiver and at the remote point and two-way telephonie communication is established with the remote point all under thecontrol of the volume control means of the radio receiver. f

10. In combination, a radio receiver comprisinga signal circuit and a reproducer, a second reproducer located a'tfapoint remote from the y receivenand a control unit for selectively connecting both of Isaid reproducers in the output o! said signal circuit-or said reproducers alternately to aninterme'diate point and to the output of said signal circuit,'one` of said reproducers lbeing con- 1 nectedfto the intermediate point when the other to the intermediate point when the other is connected tothe output, said control unit comprising means for simultaneously connecting both of said-reproducers inthe output'of said signalcircuit for the simultaneous reproduction of radio signals at the receiver and at the remote point.

12. In combination with a radio receiver hav- .ing an audioamplifier, a power amplifier, and a reproducer, a second -reproducer located at .a point remote from said receiver, a` control unit, connections from the input of the audio amplifier andfromthe output ofthe power amplifier to said control unit; connections from each of said reproducer-s to said control unit, said control unit comprising multi-position. switch means operable in one position to connect'both of said reproducers to the connections from the output of the power amplifier, in another position to connect the-reproducer of the receiver to the connections from the' outputV of the power amplifier and the remote-reproducer to the connections from the input of the audio -amplifier and said switch means being operable ina third position to connectthe remote reproducer to the connections fromthe output of the power amplifier and the reproducer of .the receiver` to the connections from the'input of the audio amplifier.

13. In combinationwitha radio'recelver` having an audio amplifier, a power amplifier, and a reproducer, a second `reproducer located at a point remote from said receiver, a control unit, connections from the input of the audio amplifier and from the output of the power amplifier" to said control unit, connections from each of said' reproducers to said control unit, said control unit comprising multi-position switch means operable in one position to connect both of said reproducers to the connections from the output of the power amplifier, in another position to connect the reproducer ofthe receiver to the connections from the output of the power amplifier and the remote reproducer to the connections from the input ofthe audio amplifier and .said switch..

means being operable in a third positionrto connect the remote reproducer'to the connectionsl from the `output of the power amplifier and the reproducer` of the receiver to the connections from the inputvof the audio amplifier; and signalling means at the remote point adapted Yto'transmit over the connections from the remote reproducer said volume control means and the input circuit to the control unit a calling signal which is impressed by said control unit on the reproducer of the receiver.

14. In combination with a radio receiver having an audio'amplifier, a power amplifier, and a reproducer,y a second reproducer located at a point remote from said receiver, a control unit, connections from the input of the audio amplifier and from the output ofthe power amplifier to .said control unit, said'control unit comprising multi-position switch means operable in one position to connect both of saidreproducers to the connections from the output of the power amplinen in another position to connect the reproducer of the receiver to the connections from the output of the power amplifier andthe remote reproducer to the connections from the input of the audio amplifier and ,said switch means being operable in a third position to connect the remote reproducer to the connections from the output of the power amplifier and the reproducer of the receiver to the connections from the input of the audio amplifier, y,and Ymeans for normally urging said switch means to its first position wherein both of said reproducers are connected to the output of the power amplifier. Y

l5. Incombination, a radio receiver comprising an audio amplifier, a. power amplifier and a reproducer, said audio amplifier comprising a thermionic tube having a controlling grid and volume control means connected to said grid, a second reproducer located at a point remote from the receiver, a control unit, connections from the control unit to the audio amplifier at a. point between the volume control means and the controlling grid of the thermionic tube, connections from the output of the'power amplifier .to said control unit, connections from each of said reproducers to said control unit, said control unit comprising multi-.position switch means operable in one position to connect both of saidreproducers tothe output of the power amplifier, in another position to `connect the reproducer of the receiver to the output of the power amplifier and the remote reproducer to the controlling grid lof the thermionic tube, and said switch means being operable in a third position to con- -nect the remote reproducer to the output of the power amplifier and the reproducer of the re- ;:e/eer to the controlling grid of the thermionic 16. In combination,` a radio receiver comprising an audio amplifier, a power amplifier and a reproducer, said audio amplifier comprising a thermionic tube having a controlling grid and volume control means connected to said grid, a second reproducer located at a point remote from the receiver, a control unit, connections from the control unit to the audio amplifier at a point between the volume control means and the controlling grid of the thermionic tube, connections from the output of the power Aamplifier to said control unit, connections from each of said reproducers to said control unit, said control unit comprising. multi-position .switch means operable in one position to connect both of said reproducersto the output of the power amplifier, in another position to connect the reproducer of the receiver to the output of the power amplifier and theremote reproducer to the controlling grid of the thermionic tube, and said switch means being operable in a third position to connect the remote reproducer to the output of the power amplifier and the reproducer of the receiver to the controlling grid of the thermionic tube, said n control unit comprising means for disconnecting the volume rcontrol means from the controlling grid of the thermionic tube when either of said reproducers is connected to said controlling grid.

two-way telephonie communication between saidv t distant points, said unit comprising a ,three-position switch means, means connecting said switch means to a point between the detector and audio-amplifier of the radio receiver, a socket for receiving the plug of the reproducer of the receiver, said socket being connected to said switch means, means including a plug for connecting said switch means to the output socket of the audio-amplifier of the receiver and means connecting said switch means to the additional remotely located reproducer, said switch means including contacts adapted selectively to connect both of said reproducers to the output socket o1' the audio-amplier or either one of said reproducers to the output `socket of the audio-amplifier and the other of said reproducers to the point between the detector and audio-amplifier whereby radio signals may be simultaneously transmitted to said reproducers or two-way telephonie communication may be established between the receiver and the remotely located reproducer.

18. In combination with a radio receiver having an audio amplifier, a power amplifier, and a reproducer, a second reproducer located at a point remote from said receiver, a control unit, connections from the input of the audio amplier and from the output of the power amplifier to said control unit, connectionsfrom each of said reproducers to said control unit, said control unit comprising multi-position switch means operable in one position to connect both of said reproducers to the connections from the output of the power amplifier, in another position to vconnect the reproducer of the receiver to the connections from the output of the power amplifier and the remote reproducer tothe connections from the input of the audio amplifier and said switch means being operable in a third position to connect the remote reproducer to the connections from the output of the power amplier and the reproducer of the receiver to the connections from the input of theaudio amplifier, a call signal generator, means associated with the remotely positioned reproducer including connections to said multi-position 'switch means for operatively connecting said call signal generator to the reproducer of the receiver when said multiposition switch means is in its first or second position, said connections being broken `by said multi-position switch'means when in its third position to prevent impression of a call signalen the reproducer of the receiver whenconnected to the input of the audio'ampliner.

t WILLIAM J. SCHNELL. 

